Abstract— The splitting concrete specimens exhibit several advantages, e.g., compactness and lightness, and the weight of the specimen can be disregarded in the calculation of fracture parameters. Existing design codes contain formulas that do not consider size effect in calculations of the tensile strength of concrete. However, it is well known that strength of concrete structures generally decreases with increasing structure size. Size effect in concrete structures can be well explained by fracture mechanics. The experimental investigations on fracture mechanics of cement-based materials until 1970s indicated that classical linear elastic fracture mechanics (LEFM) is no longer valid for quasi-brittle materials such as concrete. This inapplicability of LEFM is due to the existence of a relatively large inelastic zone in front and around the tip of the main cracks in concrete. This so-called fracture process zone (FPZ) is ignored by LEFM. Consequently, several investigators have developed deterministic fracture-mechanics approaches to describe fracture-dominated failure of concrete structures. The size effect law and the modified size effect law suggest that size effect is primarily related to a relatively large FPZ in concrete. In this study, two series of different sizes of geometrically similar square prismatic mortar specimens with maximum aggregate size=4 mm are tested by side and diagonal splitting loading. Based on 21 test results, maximum loads obtained from the test results are analyzed using both the size effect law (SEL) and the modified size effect law (MSEL). Approximate formulas based on the SEL and MSEL are developed for predicting the split-tension strength of square prismatic mortar members. Consequently, the results of the approximate formulas look viable and very promising.
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